Since a polyamide-imide has high heat resistance and chemical resistance, it is widely used for applications such as films, electric wire coating materials, molding materials, and adhesive materials.
As methods of production of the polyamide-imide, three methods are known: an isocyanate method, an acid chloride method, and a direct polymerization method.
The isocyanate method is a method of reacting imidodicarboxylic acid, synthesized from aromatic tricarboxylic acid anhydride or aromatic tricarboxylic acid anhydride/aromatic diamine (molar ratio 2/1), with aromatic diisocyanate (for example, Patent Documents 1 to 3).
The acid chloride method is a method of reacting substantially equimolar amounts of aromatic tricarboxylic acid anhydride chloride and aromatic diamine in an organic polar solvent (for example, Patent Document 4).
The direct polymerization method is a method of directly reacting aromatic tricarboxylic acid or a derivative thereof (excluding an acid chloride derivative) and aromatic diamine in the presence of a dehydration catalyst (for example, Patent Document 5).